Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS62 KGSP 190847

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
347 AM EST Sun Nov 19 2017

Cool high pressure builds into the area today and moves east of
the area Monday. A weak cold front crosses the area Tuesday night.
Low pressure develops along the Gulf Coast Thursday then moves up
the Atlantic Seaboard through the weekend.


As of 310 AM EST Sunday: The cold front and associated convection is
quickly moving east and will be out of the area before 4 AM. The
cold air is not infiltrating as fast but will still expect snow
levels to drop toward morning with rain changing to snow across the
highest peaks. Still looks like any accums should be limited to
elevations above 4000` near the TN border, if not 5000`, and even
there less than an inch is expected. Winds have increased across the
mountains and will remain very windy through the morning. The wind
advisory is well placed. Breezy conditions expected outside of the
mountains. Clearing skies expected for all but the TN border
counties where the moisture and upslope NW flow remains. Highs will
be 10 to 15 degrees below normal mountains and 5 to 10 degrees below
normal elsewhere.

Winds diminish across the mountains through the evening and skies
clear across the TN border. Clear skies and light winds expected
elsewhere. Lows will be around 10 degrees below normal across the
mountains and 5 to 10 degrees below normal elsewhere.


As of 220 AM Sunday: Short wave ridging over the area Monday moves
east Tuesday as a trough develops over the MS River valley. The flow
then splits as a northern stream short wave crosses the Great Lakes
and a southern stream short wave digs the southern end of the trough
to the Gulf Coast. At the surface, the center of high pressure
crosses the area Monday and into the Atlantic Monday night. The high
remains ridged into the area from the east on Tuesday. Southerly
flow develops between the high and a weak cold front moving into the
OH valley. Moisture does increase with this flow, but it is very
shallow. There is some insentropic lift, but it is also shallow and
relatively weak. There is some weak short wave energy crossing the
area but little to no deep forcing develops. The NAM is the fastest
with developing precip, so have trended later toward the other
guidance. This should keep p-types liquid with the later onset.
Still, PoP is limited to slight chance with very low QPF.

The cold front crosses the area Tuesday night with cyclogenesis off
the Carolina coast. There is some precip response mainly across the
I-77 corridor as a result. Again, the moisture is not deep and
forcing is weak. Therefore, have kept PoP in the slight chance range
with very low QPF. Drier high pressure begins to move in Wednesday.

Highs will be around 5 degrees below normal Monday and Tuesday then
rise to near normal Wednesday. Lows a little below normal Monday
night rise to a little above normal Tuesday night.


As of 130 AM EST Sunday: Guidance is finally beginning to come into
better agreement on overall pattern evolution around Thanksgiving.
Longwave troughing will dominate the east coast while a cutoff low
forms in the northern Gulf of Mexico late Wednesday through
Thursday. The exact track of this low remains uncertain, but trends
are now keeping it farther to our south hugging the N FL then SE
coast, keeping most of the moisture and QPF response out of our
forecast area. The moisture from this low will remain near the
Carolina coast for another day or two, with dry surface high
pressure able to work into our forecast area Friday as the upper
trough axis and a robust shortwave cross the Appalachians. An
Alberta clipper-type system will drag a cold front towards us late
Saturday and early Sunday, with cold air and deep upper troughing to
follow late in the weekend. At this point, any moisture associated
with the system looks quite anemic and confined only to our far
western mountain zones, where the possibility of light rain/snow mix
or a few snow showers is currently advertised.

After a chilly Thanksgiving with temperatures roughly 10 degrees
below average, highs and lows will moderate back to near climo
before the next cold front approaches late next weekend.


At KCLT and Elsewhere: A mixture of VFR/MVFR leading into solid
VFR through this taf period at all sites.  A fast moving cold
front is currently moving across the region with a rather dynamic
llj along/ahead of the boundary.  Therefore continued with 40kt
2kft llws mention at all sites aside for KAVL given passage.
Flow will veer wly/nwly behind the front, with gusts subsiding for
a few hours.  As for the convection itself, precip timing at each
site was based on camguide and current radar coverage, with all
sites dry by 08z at the latest.  Skies/cigs will remain at low VFR
levels through much of the overnight aside for when heavier precip
is ongoing with MVFR cigs favored via tempos.  Toward sunrise skies
will clear out rather rapidly with nwly winds increasing yielding
low end gusting amidst improving caa through mid/late afternoon.
That said, with moist upslope flow favored along the TN line,
did hold onto MVFR stratus at KAVL as upstream clouds advect down
valley until around midday.

Outlook: Expect VFR from Sunday morning through at least the middle
of next week, under the influence of cold continental high pressure.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High  87%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  94%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     Low   58%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High  94%     High 100%     High 100%     High  83%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:


GA...Wind Advisory until noon EST today for GAZ010-017.
NC...Wind Advisory until noon EST today for NCZ033-048>053-058-059-


LONG TERM...Carroll
AVIATION...CDG is the U.S. government's official web portal to all federal, state and local government web resources and services.